AB1342 THE EVALUATION OF 18F-PET-CT USE IN RHEUMATOLOGY CLINICAL PRACTICE WITH DEMOGRAPHIC AND CLINICAL FINDINGS
Authors: M. C. Ataca, S. Gulle, Y. Erez, G. Can, E. Derebek, F. Onen
Journal: Annals of the Rheumatic Diseases (2022)

Background There is an increasing number of studies in the literature on the use of 18 F-FDG-PET/CT in the diagnosis and treatment follow-up of inflammatory rheumatic and musculoskeletal diseases (iRMD) (1). PET/CT do have an important place in the diagnosis of large-vessel vasculitis (LVV), which shows increased involvement in the walls of large vessels (2). Objectives In this study, the aim was to evaluate the demographic, clinical, and laboratory characteristics, compatibility of PET/CT with other imaging methods, and the role of PET/CT in treatment follow-up of the patients who underwent PET/CT at the Rheumatology Clinic between 01.01.2010 and 31.12.2020. Methods The patients’ age, gender, comorbidities, iRMD types, medications, PET/CT, and ages at the time of iRMD diagnosis were collected. In addition, the compatibility of PET/CT with other imaging methods (MR angiography, Doppler US, and CT angiography) was evaluated in vasculitis subgroups. Control PET/CT images of the patients were evaluated by comparing them with previous imaging findings. Results A total of 280 patients, 179 (63.9%) women, with a mean age of 58±15 years, underwent PET/CT in the rheumatology department. 202 (72.1%) patients had a diagnosis of iRMD before PET/CT. After PET/CT, 40 (48.2%) patients were diagnosed with a new iRMD, and 43 (41.8%) were diagnosed with a non-iRMD. No rheumatic disease was detected in 33 (11.8%) patients. iRMD diagnosed by PET/CT are respectively; LVV (n=11), IgG4-RD (n=10), sarcoidosis (n=9), and other (n=10). It was determined that 22 (26.5%) of newly diagnosed patients other than iRMD had malignancy [Bronchial (n=8), lymphoma (n=3), breast (n=3), other (n=8) cancer]. PET/CT revealed lymphadenopathy (LAP) in 119 of 165 patients who underwent the scan to exclude malignancy, and 22 of 91 patients who underwent PET/CT for rheumatologic diagnosis. LAP was found in 45% of those diagnosed with iRMD and 74.4% of those diagnosed with non-iRMD (p=0.002). PET/CT imaging was performed on 18 patients for follow-up. The treatment of 4 out of 18 patients with follow-up PET/CT and 76 out of 280 total patients was changed after imaging. In patients with a diagnosis of giant cell arteritis (GCA), the compatibility of PET/CT with MRA was 62.5%, while its agreement with CTA was 100%, and with Doppler US was 40%. In patients diagnosed with Takayasu’s arteritis, the compatibility of PET/CT with MRA was 40%, while its compatibility with CTA was 50% and with Doppler USG was 38%. Conclusion PET/CT imaging was found to be an important adjunctive examination in the diagnosis and follow-up of sarcoidosis, LVV, and IgG4-RD in patients evaluated in the rheumatology clinic. It has been observed that it is often used in the diagnosis and follow-up of RA, SpA, and autoinflammatory diseases, to investigate the malignancies accompanying rheumatic diseases and to evaluate the characteristics of LAP. PET/CT findings provide significant benefits to the clinician in the early diagnosis of iRMDs and differentiation of malignant and/or infectious etiologies. References [1]Jamar F, et al. EANM/SNMMI Guideline for 18 F-FDG Use in Inflammation and Infection. J Nucl Med. 2013 Apr;54(4):647–58. [2]Schönau V, et al. Ann Rheum Dis. 2018 Jan;77(1):70–7. Table 1. Demographics Age (mean±SD. ) 58±15 Female/Male 179 (63.9)/101 (36.1) CRP (mg/L), median (Min.-Max. ) 16.9 (0.2-431) ESR (mm/h), median (Min.-Max. ) 43 (1-120) iRMD Subgroups, n (% ) Connective Tissue Disease 70 (28.4) Vasculitis 63 (25.5) Rheumatoid Arthritis 28 (11.3) İgG4-RD and Retroperitoneal Fibrosis 22 (8.9) Spondyloarthropathies 21 (8.5) Sarcoidosis 16 (6.5) Polymyalgia Rheumatica 8 (3.2) Others (Autoinflammatory Fever Syndromes, Crystal Arthropathies, CVID ) 19 (7.7) Reason for PET/CT scan, n (% ) For Rheumatologic Diagnosis 91 (32.5) Scan to Exclude Malignancy 165 (58.9) Treatment Response Evaluation 24 (8.6) PET/CT SUV max Values iRMD SUV max , median (Min.-Max. ) 4.6 (3.3-7.2) Malignancy SUV max , median (Min.-Max. ) 8 (6.1-10.6) *iRMD: inflammatory rheumatic and musculoskeletal diseases Disclosure of Interests None declared